Refrigerating system



Dec. 8, 1936. H. B. HULL REFRIGERATING SYSTEM Original Filed June 30, 1928 2 Sheets-Shget 1 Dec. 8, 1936. H. B. HULL REFRIGERATING SYSTEM Original Filed June 30, 1928 2 Sheets-Sheet 2 -gvuwyy gwownl oz Patented Dec. 8, 1936 attains Rnrmcnnermc srs Harry B. Hull, Dayton, Ohio, or, by time assignments, to General Motors Corpcraticn, a corporation of Delaware Application June so, 1928, Serial No. ceases Renewed December 10, 1935 p 11 Claims.

'I'his invention relates to refrigeration, particularly to an improved method of and means for operating refrigerating elements at high efliciency.

One of the objects of the invention is to prevent the accumulation of frost on refrigerating elements.

Another object of the invention is tooperate a refrigerating system cyclically in response to the frost condition of the refrigerating element.

. Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a diagrammatic illustration of a refrigerating system embodying the invention;

Fig. 2 is a diagram of the invention applied to a plurality of refrigerating devices; and

Fig. 3 is a section of a control valve.

It is usual to refrigerate rooms, compartments, cabinetsvand the like by placing a refrigerating element, such as an evaporator in the space tobe cooled and circulating refrigerant through the refrigerating element to chill the element and induce circulation of air in the space to be cooled. The refrigerating element soon becomes coated with frost formed by the freezing water condensed on the element from the circulating air, and this frost forms a resistance to the transfer of heat from the air to the element and thusreduces the efliciency of the system. Since the refrigerating requirements of the space vary from time to time and since refrigeration is pro duced by the apparatus at a fairly uniform rate which rate must be slightly higher than the maximum requirement of the space to be cooled,

it is usual to operate the refrigerating system intermittently in order to prevent cooling the space below the desired temperature.

It is one of the objects of this invention to automatically defrost the refrigerating. element whenever it becomes coated with frost so as to keep the element bare and thus permit it to absorb heat at its most eflicient rate and also to utilize the periodic frostingand defrosting of the refrigerating element for effecting the intermittent or cycling operation of the refrigerating system. p

Referring to Fig. 1, l0 designates a refrigerating element for cooling the compartment ll, 'the refrigerating element being shown for the sake of illustration, as including a header l2 forming a reservoir for volatile refrigerant, ducts l; for

circulating refrigerant and thermally conductin fins id in contact with the ducts. Liquid refrigerant is supplied to the header by a liquid conduit l6 and the evaporated refrigerant is withdrawn from the header by a vapor conduit ll, 5 both conduits being suitably connected to a condensing element including a condenser 20, a com-. pressor l9, and a motor 21 for operating the compressor. The motor is supplied with current 'nected through a conduit 28 to the bulb 26-. The bulb 26 contains water while the remaining space in the bellows and conduit 28 is filled with oil.

The apparatus above described operates as through the mains 23 under the control of a 10 follows. When the space to be cooled is warm 20 the water invthe bulb 26 is liquid and the bellows 277 is collapsed toclosethe switch. This operates the compressor to supply refrigerant to and vaporize the refrigerant in the evaporator. As the refrigerant evaporates, the compartment is gradually cooled by the circulation of the air which is chilled and circulated by the evaporator. As the air continues to circulate over the evaporator the latter is coated with frost.

The frost builds up first on the coldest parts of 30 the evaporator, namely; the header l2 and tubes 53, the fins it being the last to become coated because they are kept relatively warm by the air circulating over them. As this air becomes evaporator structure. When frosthae covered the bulb 26 it forms an insulating coating which retards the transfer of heat from the air to the bulb and permits the withdrawal of the latent heat of the water through the metallic connections from the water to the refrigerant. The

' water then freezes and in expanding exerts pressure on the oil to expand the bellows and open the switch, stopping the compressor and stop- .ping circulation of refrigerant in the evaporator.

Air continues to be circulated throughout the comparment because the evaporator is colder than the air surrounding it. relatively warm air graduallymelts the ice within the bulb 26, which reduces the pressure and allows the l bellows to collapse and close the switch to start the compressor again.

. Fig. 2 shows the invention applied to a plurality of compartments to be cooled, designated by 3| and 32. Refrigerating elements Illa and lb are colder frost gradually builds upover the entire 35 placed in the respective compartments and connected in parallel circuit relation between liquid conduit l6 and the vapor conduit ll of the condensing element, the compressor I9 which is actuated by the motor 2| and controlled by the switch 24' actuated by a metallic bellows 40 in response to the pressure in. the vapor conduit.

In the independent circuit of each evaporator preferably between the evaporator and the vapor conduit is placed a shut-off valve generally designated 4|. The valve construction is shown in Fig. 3 in which 50a and 501) are passages communicating with the evaporator and the vapor conduit II" respectively, and communicating with each other through an opening 5| which is un-\ der the control of valve 52 urged to open position by spring 53. A metal bellows 54 surrounds the valve stem and is sealed to the stem and to the valvehouslng. Surrounding the bellows is a casing 55 forming aclosed chamber which is in communication through an opening 56 with the conduit 28 connected to the bulb 26. The bulb 26' contains water and the conduit and casing 55 are filled with oil. Whenever the water in the bulb 26' freezes the pressure transmitted through the oil collapses the bellows to close the valve against the action of the spring and whenever the ice is melted the pressure falls and allows the spring to open the valve.

When either of the chambers 3| or 32 is warm, the water in its bulb 26' is melted and its valve 4| is open. Likewise the refrigerant within the header |0a or |0b is warm and consequently at high pressure. This pressure exists in the conduit i1 and expands the bellows 40 to close the switch and start the compressor. Refrigerant is circulated through the evaporator or evaporators whose valves 4| are open, thus each evaporator is refrigerated until it becomes coated with frost at which time its corresponding shut-off valve will be closed by the freezing thermostat. Thus the refrigerant will be circulated in eachevaporator in response to its frost conditions independently of what is going on in the other evaporator and will refrigerate its compartment as described in connection with Fig. 1. When both evaporators have become frosted both shut-off valves 4] will be closed and the pressure within the vapor conduit II will immediately drop collapsing the bellows 40 and opening the switch to stop the compressor.

Thereafter when either evaporator becomes defrosted, its valve will open, and the pressure of the refrigerant will close the switch to repeat the operation.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms 'might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. Refrigerating apparatus comprising in combination a refrigerating element, means for ciry culating refrigerant in the element, a motor for air, means for circulating refrigerating medium and spaced from the thin metal walls of the refrigerating element enclosing the refrigerating medium but in metallic thermal communication therewith, said last mentioned means being responsive to the frosting of the refrigerating .element for stopping the circulation of refrigerating medium through the refrigerating element and responsive to the defrosting of the refrigerating element for circulating the refrigerant medium through the element.

3. Refrigerating apparatus comprising in combination a refrigerating. element having thin metal walls enclosing the refrigerating medium, said refrigerating'element being exposed to ambient air, means for circulating refrigerating medium through the refrigerating element, and means including a thermo-bulb exposed to the ambient air and spaced from the thin metal walls of the refrigerating element enclosing the refrigerating medium but in metallic thermal communication therewith, said last mentioned means being responsive to the frosting of the refrigerating element for controlling the circulation of refrigerating medium through the refrigerating element.

4. Refrigerating apparatus comprising in combination a refrigerating element having thin metal walls enclosing the refrigerating medium, said refrigerating element being exposed to ambient air, means for circulating refrigerating me-'- dium through the refrigerating element, and means including a thermo-bulb exposed to the, ambient air and spaced from thethin metal walls of the refrigerating element enclosing the refrigerating medium but in metallic thermal commu-' nication therewith, said .last mentioned means being responsive to the frosting of the thermobulb for controlling the circulation of refrigerating medium through the'refrigerating element.

5. Refrigerating apparatus including a ,compressor, a condenser and an evaporator connected in a closed circuit, means for driving the compressor, and means for controlling the operation of the compressor including a thermostatic bulb exposed to the ambient air, in metallic thermal communication with the evaporator, and so positioned with respect to the evaporator that the frosting of the thermostatic bulb automatically stops the operation of the compressor and the defrosting of the thermostatic bulb automatically starts the operation of the compressor.

6. Refrigerating apparatus including a refrigerating element having metal walls enclosing a refrigerating medium, said refrigerating element being exposed toambient air containing water vapor, means for circulating refrigerating medium through the refrigerating element, means for normally controlling the circulation of refrigerating medium, and means including a fixed thermostatic bulb adjacent but outside of the metal walls of the refrigerating element, said last mentioned means being operable upon the accumulation of suflicient frost upon the metal walls of the refrigerating element to contact the thermostatic bulb for stopping the circulation of the refrigerating medium when frost accumulates upon the element to a certain degree, said means preventing the circulation of the'refrigerating medium until the refrigerating element is defrosted.

7. Refrigerating apparatus including a refrigerating element having metal walls enclosing a refrigerating medium, said refrigerating element lation of refrigerating medium through theele ment until the accumulated frost has melted from the unit; a

8. Refrigerating apparatus including a refrigerating element having metal walls'enclosing a refrigerating medium, said refrigerating element being exposed to ambient air containing water vapor, means for circulating refrigerating medium through the refrigerating element, control means having one position for stopping the circulation of refrigerating medium through said element, said control means when in said position Y having means efiective to stop the circulation,

said control means having another position providing circulation of refrigerating medium through said element, said control means when in said another position having means effective to render said stopping means ineffective, said control means. bymeans incorporated therein, being yieldingly held in either of saidabove mentioned positions, said control means having a thermal sensitive actuating means so positioned with respectto said metal refrigerant enclosing walls of said refrigerating element that the frosting of-the metalenclosing walls of said element will cause frost to contact the thermal sensitive actuating means to thereby cause the control means to assume one of said positions and the defrosting of said walls through the effect upon the thermal sensitive actuating means will cause the control means to assume the other of said P sitions.

9. Refrigerating apparatus comprising in combination an evaporator and means for circulating refrigerating .medium through said evaporator, means for controlling the operation of said circulating'means, and means adjacent said evaporator for modifying the circulation of refrigerating medium through, said evaporator, said last named means being rendered operative to modify said circulation upon the accumulation of sufiicient frost on the evaporator to contact said modifying means.

10. Refrigerating apparatus comprising in combination an evaporator, means for circulating a refrigerating medium through the evaporator,; means for maintaining the evaporator temperature substantially constant, means for causing the temperature of said evaporator to rise above 32 F. to thereby meltfrost from the evaporator, said last named means being rendered operative by the accumulation of suflicient frost on the evaporator to contact said second named means.

11. Refrigerating apparatus comprising incombination an evaporator and means for circulatingrefrigerant through said evaporator, means for controlling the circulation of refrigerant to thereby control the temperature of the evaporator, said last named means being rendered operative to modify the circulation when suflicient frost accumulates on the evaporator to contact a portion of said control means, said last named meansbeing rendered inoperative to modify the circulation as soon as the evaporator becomes entirely defrosted. x

- HARRY B. HULL. 

